Why Does the Pentatonic Sound Good?

There are a few different ways of thinking about the pentatonic.  The first one to understand comes from the connection between chords and scales.

You probably already know the main chords in the key of C are C, F, and G.   In music theory these would be called I, IV and V or tonic, subdominant and dominant, respectively, but don’t worry too much about that just yet.

Let’s consider the idea that whenever you have one of these major chords, it would be OK to play notes from the major scale with the same name.  So,

Over C you could play a C major scale: c d e f g a b.  

Over F you could play an F major scale:  f g a Bb c d e.

Over G you could play a G major scale: g a b c d e f#.

If we pick out the notes that all three of these scales have in common, we find C major pentatonic: c d e g a.   It’s a C major scale with a couple of notes missing.  We leave out b because it’s not in F major and we leave out f because it’s not in G major.

Now it’s easy to see why C major pentatonic works with these three major chords C, F and G.  By using the pentatonic we’ve restricted ourselves to only using notes that work with all of these chords.

What about the minor chords?  In the key of C we have Dm, Em, and Am.   The chord A minor is the relative minor of C major, which means the A natural minor scale has the exact same notes as C major.  (There are several different minor scales, but we’re not going to worry about the others now.)   So C major pentatonic will work fine over Am.  Similarly, D minor is the relative minor of F major and E minor is the relative minor of G major so we know C major pentatonic will work over those too.

There’s one remaining triad (three note chord) based on thirds in C major: Bdim.  B diminished is made up of the notes: b d f.   It doesn’t come up very often, so don’t worry about it too much.  Notice it has the two excluded notes from the pentatonic scale, b & f, and they make a tritone (flatted fifth).  The pentatonic scale doesn’t have any tritones. We’ll soon see that in some ways pentatonic scales are the most consonant, and don’t really work that well over the dissonant diminished chords.  But in the key of C this chord is usually functioning as a G7, which is kind of like a G, so for now let’s say you can use C major pentatonic over Bdim too.

So the major pentatonic works because it restricts our note choices to only those notes that work with every chord in the major key we’re in.

Next: The Circle of Fifths